Degradable materials are being investigated for a wide variety of packaging applications to ameliorate the environmental problems associated with conventional, non-degradable packaging plastics, such as polypropylene, polyethylene, poly(vinyl chloride) and polyethylene terephthalate. A promising degradable packaging material is polylactide. When contacted with water, polylactide depolymerizes and decomposes into naturally occurring substances, such as lactic acid, and ultimately can be reduced to water and carbon dioxide. This process is facilitated by heat such as is found in composting.
In typical packaging applications, a desirable degradable packaging material requires a high degree of flexibility and a high impact strength. The amorphous and semi-crystalline forms of polylactide lack these properties. Amorphous and semi-crystalline polylactide have a low impact strength. Both semi-crystalline and amorphous polylactide have a low degree of flexibility.
One method for altering the properties of polylactide to provide greater impact strength is to blend polylactide with non-degradable elastomers or to copolymerize lactide blocks with elastomeric blocks. The elastomeric phase in the composition absorbs the impact energy and thereby improves the impact strength of the polymeric materials. Although such blends are more flexible than semi-crystalline polylactide, they nonetheless have a Young's modulus that is too high for many packaging applications. Additionally, the elastomers commonly employed are not degradable, which is unacceptable for degradable packaging materials. All of the components of a degradable packaging material should be capable of substantially complete degradation.
There is thus a need for a degradable film that has a high degree of flexibility and a high impact strength.
Another need is for a degradable packaging film whose components are each degradable in the environment.
Yet another need is for a degradable polylactide packaging film having a high degree of flexibility and a high impact strength. A related need is for a degradable lawn/ trash bag having a high degree of flexibility and a high impact strength.